This section provides background information related to the present disclosure which is not necessarily prior art.
Supported olefin polymerization catalysts are of great use in industry. Hence, there is interest in finding new supported catalyst systems that increase the commercial usefulness of the catalyst and allow the production of polymers having improved properties.
Catalysts for olefin polymerization are often based on cyclopentadienyl based transition metal compounds as catalyst precursors, which are activated either with alumoxane or with an activator containing a non-coordinating anion.
Porous inorganic solids have found great utility as catalysts and separation media for industrial application. In particular, mesoporous materials, such as silicas and aluminas, having a periodic arrangement of mesopores are attractive materials for use in adsorption, separation and catalytic processes due to their uniform and tunable pores, high surface areas and large pore volumes. The pore structure of such mesoporous materials is large enough to adsorb large molecules and the pore wall structure can be as thin as about 1 nm. Further, such mesoporous materials are known to have large specific surface areas (e.g., 1000 m2/g) and large pore volumes (e.g., 1 cc/g). For these reasons, such mesoporous materials enable reactive catalysts, adsorbents composed of a functional organic compound, and other molecules to rapidly diffuse into the pores and therefore, can be advantageous over zeolites, which have smaller pore sizes.
Consequently, such mesoporous materials can be useful not only for catalysis of high-speed catalytic reactions, but also as large capacity adsorbents.
Mesoporous organosilica (MOS) supports are conventionally formed by the self-assembly of a silsequioxane precursor in the presence of a structure directing agent, porogen and/or framework element. The precursor is hydrolysable and condenses around the structure directing agent. For example, Landskron, K., et al. report the self-assembly of 1,3,5-tris[diethoxysila]cylcohexane [(EtO)2SiCH2]3 in the presence of a base and the structure directing agent, cetyltrimethylammonium bromide. Landskron, K., et al., Science, 302:266-269 (2003). The citation of references herein does not constitute an admission that those references are prior art or have any relevance to the patentability of this description disclosed herein. All references cited in the Background and Description sections of this specification are hereby incorporated by reference in their entirety.
However, the use of a structure directing agent, such as a surfactant, in the preparation of an organosilica material, such as a MOS, requires a more complicated, energy intensive process that limits the ability to scale-up the process for industrial applications. Additionally, structure directing agents present during formation impact the morphology of the organosilica material product. Furthermore, introduction of additional agents or processing steps to remove structure directing agents from MOS can introduce additional reactive and undesirable compositions into the system, potentially leading to additional species that could cause catalyst poisoning.
There remains a need in the art for new and improved supported catalysts and catalyst systems for the polymerization of olefins to obtain new and improved polyolefins, polymerization processes, and the like. Such new and improved catalyst systems can desirably achieve specific polymer properties, such as high melting point, high molecular weights, increasing conversion or comonomer incorporation, or altering comonomer distribution without deteriorating the resulting polymer's properties. Thus, there is a need to provide organosilica materials having desirable pore size, pore volume and surface area, which can be prepared in the absence of a structure directing agent, a porogen and/or a framework element (aside from C, O, Si and hydrogen). Such materials will be described further herein. For more information, see also, U.S. Provisional Application No. 62/091,071 filed on Dec. 12, 2014 and U.S. Provisional Application No. 62/091,077 filed on Dec. 12, 2014, the disclosures of which were fully incorporated herein by reference above. Accordingly, new and improved supported catalyst systems for the polymerization of olefins are contemplated by the present disclosure, in order to achieve enhanced properties, such as molecular weight, and/or comonomer incorporation, typically along with improvements in catalyst function, such as activity, by way of non-limiting example.